The present disclosure herein relates to a tactile display device, and more particularly, to a tactile display device using an electroactive polymer.
An electroactive polymer (EAP) is a material, which is modified when external voltage is applied thereto, and is now attracting much attention because of many advantages such as weight reduction, slimness, and miniaturization due to an good processability of the polymer material, as well as rapid response rate, large actuation displacement, and low power consumption in operation. The EAP may be applied to haptic phones, haptic mouse, camera modules, flat speakers, and tactile sensors, etc. Further, unlike materials such as metals or ceramics, the EAP has elasticity and strength similar to those of human muscle, so that the EAP is applicable as artificial muscle or biomimetic actuators.
Mostly, EAPs are divided into two groups. That is, an ionic EAP and electronic EAP, wherein, when external voltage is applied, in the ionic EAP, shrink-expansion modification of the polymer occurs due to migration and diffusion of ions, and, in the electronic EAP, modification occurs due to electronic polarization. Examples of the ionic EAP include electrorheological fluids, carbon nanotubes, conducting polymers, ionic polymer-metal composites, and polymer gels, etc. which have various benefits such as high actuation force, rapid response rate, and low applied voltage. Examples of the electronic EAP include liquid crystal elastomers, electro-viscoelastic elastomers, electrostrictive papers, electrostrictive graft elastomers, dielectric elastomers, and ferroelectric polymers, etc. which have benefits such as rapid response rate, and an elaborate displacement modulation.
Among those mentioned above, the dielectric elastomer is beneficial in many aspects in terms of a strain, a rapid response rate, driving force, and energy storage. It may be expected that when the strain is adjusted through voltage, multi-step tactility/texture can be expressed in a thickness direction, however the recognition rate of the step may be greatly declined due to unidirectional expression and changes of entire pixels. Thus, it is required to prepare various surface shapes by an electronic field in order to use the dielectric elastomer in tactility/texture touch screen which may express various texture and tactility.